Microplastics are increasingly recognised as a significant environmental pollutant, found in oceans, rivers, soils, and even underground water systems. These tiny particles, with diameters of less than 5mm, are transported by water, can accumulate in sediments, and can be ingested by aquatic organisms (over 1,500 species have been documented to ingest microplastics), which could be passed up the food chain. Understanding the occurrence and persistence of microplastics in different environments is crucial to understanding their impacts.
As part of my research into microplastic pollution in karst groundwater, we recently conducted water and sediment sampling at Poole's Cavern. We aimed to investigate microplastics through the entire system. Sampling began at the stream sinks on the surface, which are known to be connected to the cave, where surface water enters the underground karst system. We sampled the cave stream within Poole's Cavern, both at the point where the stream enters and where it exits the tourist cave, to look for any microplastics accidently brought in by people visiting the cave, for example microfibres from clothing. We also collected samples at the Wye Head Resurgence Spring, the largest spring in the area, where water from the cave re-emerges and connects to the River Wye. This helps us to understand how any microplastics carried along in the water re-emerging from the cave system contribute to plastic pollution downstream in the river itself. A transect of sediment samples was also collected from the cave stream bed and banks to investigate the accumulation of microplastics in cave sediments. This interconnected network of sampling points will show how microplastic concentrations, sizes, shapes, and types vary as the water travels through the ground from entry to exit.
River water and sediment sampling within Pooles Cavern
Karst systems, such as those of which Poole’s Cavern is a part are particularly vulnerable to contamination from plastic pollution as their pipe-like structures allows water and any pollutants it carries to travel quickly through the system without much natural filtration. By investigating the entire flow path from stream sinks to spring, this study seeks to determine how anthropogenic activities, and geological factors affect the distribution and transformation of microplastics. Samples will be analysed using state of the art microplastic analysis methods at the UK Centre for Ecology and Hydrology (UKCEH), letting us pinpoint the presence of tiny plastic particles, even those too small for the naked eye to see.
This investigation is thought to be the first of its kind to assess microplastic presence, concentration, and characteristics within a UK cave system, and will lead to a better understanding of the impacts of microplastics in karst environments.
The study is being conducted in collaboration with the British Geological Survey (BGS) and UKCEH, and we are grateful to John Gunn and the team at Poole’s Cavern for their assistance with this project.
Maria at the upstream sampling location
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